The invention relates to the use of optical code readers to produce video displays and to detect non-code image information. Aspects of the invention are particularly useful in handheld code readers with image sensors which are in communication with a host terminal.
Most conventional optical scanning systems are designed specifically to read optical codes such as one-dimensional barcode symbols. Typical conventional scanning systems generate one or more beams of laser light which reflects off a barcode symbol and back to the scanning system. The system obtains a continuous analog waveform corresponding to the light reflected by the code along one or more scan lines of the system. The system then decodes the waveform to extract information from the barcode. A system of this general type is disclosed, for example, in U.S. Pat. No. 4,251,798, assigned to Symbol Technologies, Inc. A beam scanning system for detecting and decoding one and two dimensional barcodes is disclosed in U.S. Pat. No. 5,561,283, also assigned to Symbol Technologies, Inc.
Advantageously, barcodes and other optical codes can also be read employing imaging devices. For example an image sensor may be employed which has a two dimensional array of cells or photo sensors which correspond to image elements or pixels in a field of view of the device. Such an image sensor may be a two dimensional or area charge coupled device (CCD) and associated circuits for producing electronic signals corresponding to a two dimensional array of pixel information for a field of view. An xe2x80x9cImaging Engine And Method For Code Readersxe2x80x9d is disclosed in a patent application so titled to Correa et al., assigned to Symbol Technologies, Inc. and filed on Jun. 12, 1998 which is hereby incorporated by reference. Many scanners in use today are deployed in handheld units which may be manually pointed at the target. Often an individual scanner is a component of a much larger system including other scanners, computers, cabling, data terminals and data displays. Applicants have discovered that imaging optical code readers, particularly when used in such systems, may be adapted to have new, non-code-reading functions.
Accordingly, it is a general object of the present invention to provide imaging systems which can be employed for code reading and for a variety of functions other than optical code reading.
Further, it is an object of the present invention to adapt imaging code readers for use in video displays, surveillance and detection of physical parameters of target objects.
Various lens systems have been developed for optical code readers. Applicants assignee, Symbol Technologies, Inc. has developed bi-stable high speed zone collection systems for barcode scanners. Systems which employ lens structures moveable into the input optical path of the scanner (drop-in optics) are disclosed in U.S. patent application Ser. Nos. 08/627,167 and 08/627,168 filed Apr. 3, 1996 to Li et al. A lens structure for an imaging code reader is disclosed in the above-mentioned Correa et al. patent application. Conventionally, code reader lens systems are designed to provide a depth of field, focus and monochrome detection particularly adapted for code reading.
It is an object of the present invention to provide a simply and inexpensively fabricated objective lens system for an optical code imaging engine.
It is another object of the present invention to provide objective lens systems enabling an imaging optical code reader to be used effectively for both code reading functions and for non-coding reading functions such as color video displays and detection of physical parameters associated with a bar-coded object or its environment.
It is another object of the present invention to provide an imaging optical code reader with a field of view and working depth of view appropriate to the signal processing and decoding capabilities of the reader and with other optical fields and focal depths for other video functions.
In a number of businesses, in particular in transportation and food retail, it is desirable to decode a barcode and to determine the dimensions or size (Volume) and/or the weight of a package or item. Presently, multiple instruments and steps are required to obtain these parameters.
It is a further object of the present invention to use an imaging optical code reader system to determine such parameters.
Some or all of the objects previously described may be achieved in a single optical code reading engine or system. With the addition of appropriate control circuitry and data processing software, a system may be constructed serving the object of producing a compact, inexpensively fabricated imaging system for performing new video and image analysis functions.
These and other objects and features of the invention will be apparent from this written description and drawings.
The present invention relates to methods and apparatus useful in optical imagers, especially imaging optical code reader systems. Techniques are disclosed which are applicable to the design of imaging engines, imaging lens systems, aiming systems, code reading stations or terminals, and signal processing devices associated with imagers of various types.
An imaging and aiming apparatus for an optical code reader may be based on an image sensor, including an array of photo sensor cells for producing electronic signals corresponding to a two dimensional array of pixel information for a field of view. In preferred embodiments, the image sensor is a CCD. The image processing circuitry/software located in a handheld reader or terminal, may be employed to analyze a portion of a projected pattern. This information may be used as feedback to the processing circuitry to help identify an image area in which a target barcode is located. Such image processing may also be used for determining the distance between the reader and the target barcode or physical parameters associated with a target object or its environment.
A preferred embodiment of the present invention is a system for reading optical code for displaying video images, using essentially the same hardware.
A handheld optical code reader is provided including a two dimensional image sensor and means for compressing video data obtained from the sensor. The code reader is connected to a host terminal with a communication port and display monitor by a narrow band width data link over which compressed video data from the handheld optical code reader and decoded information from optical codes read by the handheld code reader is communicated to the serial communication port of the host terminal. In a more preferred embodiment, the system can be switched between a code reading function and a video display function. In the code reading mode, the system may be presented with a code containing the command for the system to switch to a video display function.
An example of the narrow band width data link between the handheld optical code reader and the remainder of the system may be an RS 232 cable connected between the handheld reader and a serial communication port of the host terminal. Such a link may operate, for example, at 115 k Baud to transmit a compressed 300xc3x97200 pixel image at 3-4 frames/second. Alternatively, the narrow band width data link may be a radio frequency transmitter and receiver or an infrared transmitter and receiver.
The system may further comprise circuitry/software for detecting motion in a field of view of the handheld optical code reader. In preferred embodiments, motion is detected by monitoring the bandwidth of the compressed video signal. In this way the handheld reader, can for example, be strategically positioned for security monitoring and be used to trigger an alarm or other indication of an intrusion into the field of view of the system.
Also disclosed is a related method for performing motion detection using an optical code reader. According to the method, an image sensor of the optical code reader is positioned so that a field of view of the image sensor includes a region to be monitored for motion. The optical code reader is switched from an optical code reading mode to a motion detection mode. Video data in the field of view of the image sensor is compressed by identifying changes between frames of video data, and the frequency of changes between frames of video data is monitored to identify relatively low frequency changes indicative of the movement of relatively large objects in the field of view. The method may include the further steps of transmitting the compressed video data from the optical code reader to a terminal, and displaying the image of the field of the range sensor at the terminal.
Physical parameters other than motion in the field of view of the optical code reader may be detected. The present invention includes systems for detecting optical code and, generally, one or more physical parameters of a target object. In a preferred embodiment, these systems include an image sensor for producing electronic signals corresponding to a two dimensional array of pixel information for a field of view containing the target object. A light pattern projector is provided to project a pattern such as a set of cross-hairs on objects in the field of view of the sensor. The system includes circuitry/software for reading an optical code in the field of view of the image sensor as well as for determining a physical parameter of the target object from the reflection of the light pattern from the target object onto the image sensor.
In more preferred embodiments the physical parameter of the target object is determined by measuring edge discontinuities in the light pattern caused by that target object. The system may further comprise a platform for supporting the target object in the field of view of the image sensor. An arrangement of springs or other weight sensitive structures may be provided to support the platform and permit the platform to move through a distance approximately proportional to the weight of the supported target object. A counter surface adjacent to the platform may be used to produce an edge discontinuity in the reflected pattern between an edge of the platform and an adjacent edge of the counter surface. In the case that the projected pattern is a line, a separation distance between reflected segments of the line at an edge discontinuity may be measured and used as an indication of weight based on a predetermined correlation between the two values.
In another preferred embodiment the projected pattern includes at least one line and a vertical height of an object on the platform is detected by measuring a discontinuity in the line at an upper edge of the object. In a further embodiment, the projected pattern includes two non-parallel lines. A length and width of the object on the platform is detected by measuring the length of a segment of one line lying between edge discontinuities in the direction of the length of the object, and the length of a segment of the other line lying between edge discontinuities in the direction of the width of the object, respectively.
Thus, the system may be capable of reading a code on a target object, producing a video display detecting motion in a field of view of the system, determining the distance to the target object, determining its weight, and determining its height, length and width.
This summary is provided for the convenience of the reader, it being understood that the particular subject matter which applicants regard as their invention is defined in the claims.